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Le Sphinx
Pocket cipher device · 1930

LE SPHINX 1 was a pocket cryptographic device, developed around 1930 by Société des Codes Télégraphiques Georges Lugagne in Paris (France). The device consists of 10 sliding bars with two scrambled alphabets each, and should therefore be classed as an alphabet transposition cipher. At the time, it was advertised as a method for secret writing when sending (radio) telegrams.

The device consists of a metal frame with ten lanes, each of which holds two movable rods with scrambled alphabets. The 20 transposed alphabets are identified by a number, imprinted in red, and are always used in pairs, with the upper alphabet representing the clear text and the lower alphabet used for the cipher text. 2

The rods can be moved by treaded knobs at the right side which engage gears at the bottom. Two fixed ruler windows are present for setting and reading the plain text and cipher text. The source text is processed 10 characters at a time.
Le Sphinx manual cipher system

The device is based on the 1912 invention of a mechanical pocket transposition cipher device by Georges Lugagne of Boches-du-Rhône (near Marseille, France), which was registered in 1913 as French Patent 461.217 [1]. Around the same time, the device was patented in the United Kingdom as British patent 23,204 [2]. The device was marketed in France by Lugagne's companies in Paris and Marseille, who had become known for their international telegraphic code books of 1914.

The image on the right shows the original design of 1912, which is mechanically less complex, but works very similar. It also consists of 20 paired scrambled alphabets, but they are not coupled mechanically. The sliding rods are made of ivory.

In 1931, the design was improved by Lugagne's employee Paul Godillon, who added the gears and the 10 treaded knobs at the right hand side. He was also responsible for adding the S-shaped gaps at each end of the alphabet rods, allowing the scrambled alphabets to be coupled in pairs, freely mixing the upper and lower alphabets.
The original 'Transpositeur' of 1912. Photograph by Daniel Tant [8].

Godillon's invention was patented in France on 4 Feb. 1931 [3]. The same patent was filed in the US on 1 December 1931 by Albert Gentet [4], who also added the movable index to each window [5]. It is currently unclear where Le Sphinx was manufactured and by whom, but it is possible that it was made by the famous slide rule manufacturer BARBOTHEU in Paris, who also manufactured the Transpositeur in 1912 [7]. The latter is further described in an article by Daniel Tant [8].

  1. 'Le Sphinx' is French for 'The Sphinx'. Also see the discussion about the name.
  2. This is just an assumption. There is no reason why it could not be used the other way around, as long as both parties do it in the same way.

Bakelite storage case Le Sphinx stored inside the bakelite case Close-up of Le Sphinx inside the bakelite case Le Sphinx in neutral position Le Sphinx manual cipher system Left side of the device Close-up of the knobs Holding Le Sphinx in the hand
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Bakelite storage case
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Le Sphinx stored inside the bakelite case
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Close-up of Le Sphinx inside the bakelite case
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Le Sphinx in neutral position
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Le Sphinx manual cipher system
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Left side of the device
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Close-up of the knobs
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Holding Le Sphinx in the hand

The diagram below gives an overview of the various features of Le Sphinx. The device measures just 162 x 87 x 20 mm and consist of a die-cast metal alloy frame with 10 cogwheel driven lanes, each of which accomodates two physically locked scrambled alphabets. This effectively results in 10 different transposition ciphers that allow the text to be enciphered in groups of 10 letters.

On top of the device are two horizontal windows: one for the plaintext and one for the ciphertext. The position of the rods or rulers with the alphabets can be altered by means of 10 treaded knobs at the right side. Each knob drives a cogwheel that in turn engages the teeth at the bottom of a rod. Each position has a 'click' to ensure that the letters are properly shown in the windows.

Name   Le Sphinx
The pocket cryptographic device featured on this page, was marketed by Société des Codes Télégraphiques Georges Lugagne, which had offices in Paris and Marseille (France). It is currently unclear under what name the device was sold, but since the bakelite storage case holds a raised image of a sphinx, it is commonly referred to as SPHINX. The metal label at the left side of the device shows the company name and the image of the sphinx, with the text 'LE SPHINX' (the sphinx). In order to distinguish it from the Sphinx Cipher Machine, we will call it 'Le Sphinx'.

Left side of the 'Le Sphinx' cipher device

The name 'Sphinx' originates from the Greek language and represents a mythical creature that generally consists of the body of a lion with the head of a human. In Greek tradition it may also have the wings of a bird. Sphinx' also exist in Egyptian culture (e.g. Great Sphinx of Giza) [9].

When calculating the total number of combinations that can be made with the device, we will first look at the original design of 1912. It had 20 alphabet rulers, 10 of which were intended as the upper alphabets and the other 10 were the lower alphabets [1]. This gives us 10! (or 3,628,800) possible combinations of alphabets 1 for the upper half only. As the same is true for the lower half, the total number of combinations would be 3,628,800 x 3,628,800, which is no less than:


After the design had been improved by Paul Godillon in 1931, there was no longer a differece between the upper and the lower alphabets, allowing them to be mixed freely [3]. As a result the total number of combinations in which the 20 alphabets can be mixed, increased to 20! or:


  1. 10! is the mathematical notation for 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

Before exchanging a message by means of Le Sphinx, both parties first have to agree which alphabet is used in each position. This is done by quoting the red number that is printed on the top of each rod. This is known as the settings or the key and is usually pre-arranged between the parties. For the default position, which we have used on this page, the key would be:

01 02 03 04 05 06 07 08 09 10
11 12 13 14 15 16 17 18 19 20

Both users should now install the alphabets in the order indicated on the key sheet. Each pair (e.g. 01-11) should be coupled by fitting the S-shaped gap at the top of the lower alphabet into the S-shaped gap at the bottom of the upper alphabet. For the above key, the setup would be:

Default setup. Click to enlarge.

Le Sphinx is constructed in such a way that the user can move the rulers by means of treaded knobs at the right side. There are 5 sets of two knobs. The leftmost knobs (i.e. the larger ones) are used to control the rightmost 5 lanes, whilst the rightmost knobs control the leftmost 5 lanes. Furthermore, there are two windows through which we can read a row of letters. Now rotate the knobs so that the first 10 letters of the plaintext are visible in the upper window, for example:


All you now have to do is read the ciphertext from the lower window, which in this case is:


All the receiving party has to do, is rotate the rulers so that the ciphertext is visible in the lower window. The original plaintext can now be read from the upper window.

Bottom view Close-up of the knobs (bottom view) The teeth at the bottom of each rod Plaintext Ciphertext S-shaped coupling between upper and lower alphabet
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Bottom view
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Close-up of the knobs (bottom view)
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The teeth at the bottom of each rod
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S-shaped coupling between upper and lower alphabet

Cipher security
Despite the large number of possible arrangements of the alphabets, Le Sphinx provides only low-grade cipher security. This is mainly caused by the fact that the arrangment of the alphabets does not change during the course of a message. If a message is long enough, it can be solved by frequency analysis. For very short messages, the cipher would be relatively secure though.

Another weakness of the system is that there is no provision for sending the key at the start of a message. Instead, it has to be pre-arranged. This was also the case with the German Enigma cipher machine, although in that case, procedures were in place to add a random message key.

The table below shows each of the 20 scrambled alphabets of our device. Note that the alphabets are printed in the regular order, but that they are shifted by a few positions on each ruler. Also note that the alphabets on the first 10 rulers (1-10) are in ascending order, whilst the alphabets on the last 10 rulers (11-20) are in descending order.

  1. Original Sphinx leaflet with description and operating instructions (French)
    Date unknown but believed to be 1930 (est.).

  2. Cleaned-up version of the above leaflet (French)
    Date unknown but believed to be 1930 (est.). 1
  1. Document kindly provided by Richard Brisson.

  1. Georges Lugagne, French Patent 461.217
    Filed 24 October 1913, granted 23 December 1913. Priority date 23 October 1912.

  2. George Lugagne, British Patent 23,204
    Filed 14 October 1913, granted 9 April 1914.

  3. Paul Godillon, French Patent 710,604
    Filed 4 February 1931, granted 27 August 1931.]

  4. Albert Gentet, US Patent 1,956,384
    Filed 1 December 1931, granted 24 April 1934.

  5. Albert Gentet, French patent 812.481
    Filed 1 February 1937, granted 11 May 1937.

  6. Pendergrass to Friedman, Classified files of US Patent Office
    US Government Internal Memorandum, 8 October 1953. pp. 4. 1

  7. Linialis, Règles Rares ou Originales
    Website Retrieved April 2016.

  8. Daniel Tant, Le transpositeur à permutations secrètes
    Date unknown. Retrieved April 2016 (French). 2

  9. Wikipedia, Sphinx
    Retrieved April 2016.
  1. Approved for release by NSA on 16 July 2014, E.O. 13526.
  2. Reproduced here by kind permission of the president of the
    Association des Réservistes du Chiffre et de la Sécurité de l'Information.

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Crypto Museum. Created: Friday 15 April 2016. Last changed: Saturday, 24 February 2018 - 13:14 CET.
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